Chemically-active aqueous solution and solid substance containing divalent iron ions

ABSTRACT

An aqueous solution or solid substance contains divalent iron ions and L-ascorbic acid. The L-ascorbic acid is present in an amount of 2.0 parts by weight or more per 100 parts by weight of the divalent iron ions. The aqueous solution or solid substance can be used advantageously as deodorants, germicides, foods freshness preserving agents, water treatment agents or the like.

DESCRIPTION

1. Technical Field

The present invention relates to a novel aqueous solution having various chemical effects such as deodorization, bactericidal action, preservation of freshness of foods, coagulation of pollutants, etc., and more specifically to an aqueous solution containing divalent iron ions in a stabilized state and a solid substance obtained by impregnating with the aqueous solution and then subjecting to a drying treatment.

2. Background Art

Iron (II) compounds such as ferrous sulfate have a wide variety of utility. However, when they are left over in the form of their aqueous solution, ferrous ions are, as well-known in the art, susceptible to ready oxidation by dissolved oxygen or air, whereby they turn to a yellowish brown color and result in the occurrence of a precipitate. It has been known to utilize hydroxylamine, a tin compound or the like as a reducing agent in order to avoid the oxidation of ferrous ions in aqueous solutions. These substances are however highly toxic to the human body, resulting in a limitation in the fields in which aqueous solutions containing divalent iron ions can be applied.

3. Disclosure of the Invention

An object of the present invention is to provide an aqueous solution containing stabilized divalent iron ions. Another object of this invention is to provide new uses for aqueous solutions containing stabilized divalent iron ions.

The present inventors have carried out a variety of investigations on the stabilization of divalent iron ions in aqueous solutions. As a result, it has been found that the addition of a small amount of L-ascorbic acid can unexpectedly stabilize dissolved divalent iron ions while maintaining their effective activities; that the aqueous solution containing the divalent iron ions stabilized by L-ascorbic acid exhibits, owing to a synergistic action of L-ascorbic acid and divalent iron ions, unique chemical activities unavailable from any aqueous solution which does not contain L-ascorbic acid but contains divalent iron ions, thereby providing an aqueous solution useful in a wide variety of fields; and that a solid substance obtained by impregnating a solid material with the aqueous solution and then by subjecting it to a drying treatment and containing L-ascorbic acid and an Iron(II) compound also has unique chemical activities similar to the aqueous solution, leading to the completion of the present invention.

The present invention provides a chemically-active aqueous solution characterized in that said aqueous solution contains divalent iron ions and L-ascorbic acid, the divalent iron ions are present at a concentration of 0.15 wt.% or higher as calculated in terms of metal iron in the aqueous solution, and the L-ascorbic acid is present in a proportion of 2.0 parts by weight or more per 100 parts by weight of the divalent iron ions are expressed in terms of metal iron.

The aqueous solution of present invention may be readily prepared by dissolving an iron(II) compound and L-ascorbic acid in water. As the iron(II) compound, any desired compound may be used so long as it can be dissolved in water to form divalent iron ions. For example, the water-soluble iron(II) salts of inorganic acids such as ferrous sulfate, ferrous chloride, ferrous bromide, ferrous iodide and ferrous nitrate and additionally, water-soluble iron(II) salts of organic acids such as ferrous gallate, ferrous malate and ferrous fumarate may be mentioned. The concentration of divalent iron ions in an aqueous solution is generally 0.15 wt.% or higher or preferably, 0.3 wt.% or higher as calculated in terms of the metal iron in view of the unique chemical activities of the aqueous solution. Its upper limit is the solubility of each iron (II) compound. L-ascorbic acid may be added in an amount or 2.0 parts by weight per 100 parts by weight of divalent iron ions, as expressed in terms of the metal iron in the aqueous solution. Although there is no particulsar limitation on its upper limit, it is desirable from an economical viewpoint to control it to below 30 parts by weight, with 3-10 parts by weight being preferred. If the amount of added L-ascorbic acid should become smaller than 2 parts by weight per 100 parts by weight of divalent iron ions, its effect for stabilizing the divalent iron ions will be reduced. Thus, such small amounts are not preferred.

In an aqueous solution containing divalent iron ions to which L-ascorbid acid has been added in accordance with this invention, the divalent iron ions are stabilized while maintaining their active state. Accordingly, no substantial precipitate will be formed even if the aqueous solution is kept in contact with air for a long period of time. On the other hand, the aqueous solution of the present invention may also be used by impregnating a solid material, which has hygroscopicity, with the aqueous solution. In this case, the solid material impregnated with the aqueous solution is dried to a appropriate degree, thereby causing the solid material to carry the L-ascorbic acid and the iron(II) compound. The combination of L-ascorbic acid and the iron(II) compound, which are both carried on the solid material, also exhibits such unique chemical activities as those seen with the aqueous solution.

Compared with usual aqueous solutions containing divalent iron ions, the aqueous solution of this invention shows various unique chemical activities. As such activities, it is mentioned that it has a significantly high degree of deodorizing effect against malodorous substances containing sulfur or nitrogen, for example, hydrogen sulfide, methyl mercaptan, ammonia, trimethylamine and so on. In an aqueous solution directed to the deodorizing effect, the proportion of L-ascorbic acid may range from 2 to 30 parts by weight, or preferably from 3 to 10 parts by weight per 100 parts by weight of iron(II). In this aqueous deodorant solution, it may be desirable to control the total concentration of L-ascorbic acid and iron(II) compound in the aqueous solution within 0.1-30 wt.% or preferably 1.0-20 wt.%. In order to provide a solid deodorant, this aqueous solution may be impregnated into a solid material such as paper, synthetic paper, fabric, non-woven fabric, porous filler or the like, followed by a drying treatment. In this case, the drying treatment may be omitted in some instances. As such a porous filler, may be mentioned activated carbon, zeolite, bentonite, kaolin, pearlite, sepiolite, diatomaceous earth, silica, alumina or the like. It may have a desired shape, such as powder, granules or the like. The total amount of L-ascorbic acid and Iron(II) compound to be carried on the solid material may be about 0.5-20 parts by weight or so per 100 parts by weight of the solid substance. Paper or non-woven fabric bearing L-ascorbic acid and an iron(II) compound may be discolored when left to stand in air for a prolonged period of time. Such discoloration may however be successfully avoided by additionally incorporating a thiosulfate such as sodium thiosulfate or a dithionite such as sodium dithionite in a suitable amount, for example, one tenth or less of the total amount of the L-ascorbic acid and iron(II) compound.

A deodorant composed of the above-described aqueous solution or solid substance, which is comprised of L-ascorbic acid and an iron(II) compound, may be applied for such purposes in the removal of offensive odor in toilets, garbage pails, refrigerators, drainage openings and the like and the removal of offensive odors in the spaces of room interiors. As to the application of the deodorant, it may be sprayed over each source of offensive odor or may be used as a wash solution to wash each source of offensive odor if the deodorant is in the form of an aqueous solution. If it is in a solid form, it may be applied directly to each source of the offensive odor or, the solid deodorant may be placed in the area containing the offensive odor. The above deodorant may also be used by incorporating it into a part of a sanitary material such as diaper or sanitary napkin.

As the second unique activity of the aqueous solution of the present invention, may be mentioned that it has a bactericidal action and is effective in preserving the freshness of foods. When the aqueous solution of the present invention is applied to perishable foods such as vegetables, fruits, meat, fish and shellfish, and the like, or such processed foods, these foods can be maintained with a high degree of freshness over prolonged periods of time. In this case, the aqueous solution may be applied by coating or spraying it to foods or by dipping the foods in the aqueous solution. Similar to the above-described application as a deodorant, the aqueous solution may be also be impregnated in a solid material such as paper, synthetic paper, non-woven fabric, porous filler or the like and then subjected to a drying treatment in order to convert it into a solid freshness-preserving agent. Regarding application methods of such a solid freshness-preserving agent, in the case of a sheet- or film-like form for example, it may be used to wrap foods. On the other hand, when it is in a powdery or granular form, it may be . . . a suitable drug . . . .

The above-described aqueous solution or solid substance containing L-ascorbic acid and an iron(II) compound can be used as a freshness-preserving agent. Its freshness-preserving effect can be attributed to the strong bactericidal action resulted from the combination of L-ascorbic adid and divalent iron ions. Compositions containing L-ascorbic acid and divalent iron ions may be used as germicides against Escherichia coli and other generally known bacteria.

As a further unique activity of the aqueous solution of the present invention, may be mentioned its coagulation-promoting effect for pollutants. When L-ascorbic acid and divalent iron ions are added to water contaminated with pollutants, the pollutants form floc and settle down. An aqueous solution useful as such a water treatment agent may contain L-ascorbic acid and an iron(II) compound at a total concentration of 0.01-20 wt.% or so. Its coagulation effect can be enhanced further by adding to the aqueous solution a small amount of a colloid dispersant such as zeolite, bentonite, silica flour or acid clay. A water treatment agent containing the L-ascorbic acid and iron(II) compounds are particularly superb in its coagulating effect for organic substances such as humic acid, sodium ligninsulfonate, alkali lignin and the like.

As mentioned above, the solution-like or solid-like composition according to the present invention which contains L-ascorbic acid and divalent iron ions has various unique activities. These activities can be attributed to the fact that owing to the action of divalent iron ions in the presence of L-ascorbic acid, molecular oxygen is converted to a super oxide (O₂ ⁻) having oxidizing power stronger than the original molecular oxygen upon contact with divalent iron ions. The reactions can be shown by the following equations.

    Fe(II)+O.sub.2 ⃡Fe(II).O.sub.2 ⃡Fe(III).O.sub.2.sup.-

    Fe(II).O.sub.2 +Fe(II)⃡Fe(II).O.sub.2.Fe(II)⃡Fe(III).O.sub.2.sup.-.Fe(III)

The aqueous solution of the present invention, which contains L-ascorbic acid and divalent iron ions, may be employed, besides for the above-described various unique purposes, for applications which have conventionally been known with respect to aqueous solutions containing divalent iron ions.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 to FIG. 4 are graphs showing respectively test results of Example 1;

FIG. 5 is a graph showing test results of Example 2; and

FIG. 6 is a graph showing test results of Example 3.

EXAMPLES

The present invention will hereinafter be described in further detail by the following Examples.

EXAMPLE 1

L-Ascorbic acid was added to and dissolved in an aqueous solution of ferrous sulfate (51.7 g Fe/liter), at concentrations up to 5 grams per liter.

A 100 ml portion of each aqueous solution was taken in a 100-ml beaker. The aqueous solution was left to stand in such an open system that a watch glass was merely placed as a lid on the beaker. Changes in the color of the aqueous solution and in the formation of precipitate were observed with the lapse of time.

Test results are shown in the following table.

                                      TABLE 1                                      __________________________________________________________________________     Changes of Ferrous Sulfate Added with L-Ascorbic Acid                          with the lapse of Time                                                         Days left                                                                           Concentration of L-ascorbic acid                                          to stand                                                                            0 mg/l  500      1000     2000    3000    4000    5000                    __________________________________________________________________________      1st day                                                                            yellowish                                                                              Greenish Greenish Greenish                                                                               Greenish                                                                               Greenish                                                                               Greenish                     green, cloudy                                                                          blue, clear                                                                             blue, clear                                                                             blue, clear                                                                            blue, clear                                                                            blue, clear                                                                            blue, clear              2nd day                                                                            ↓                                                                           ↓                                                                           ↓                       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                             ↓                                                                          Black-                                                                              ↓           and up                                                                              ↓                                                                           ↓                                                                           ↓                                                                            ↓                                                                           ↓                                                                            ↓                                                                           ish  ↓                                                                          ish  ↓                                                                          ish  ↓                                                                          ish  ↓             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                     ↓           __________________________________________________________________________

The, chromaticity was measured by UV-300 on each of the above-described aqueous ferrous sulfate solutions which were each treated with L-ascorbic acid. The results are shown in FIG. 1 to FIG. 4, where the absorption spectrum is shown for every passing day. The added amounts of L-ascorbic acid were respectively 0.5 g/liter, 1 g/liter and 2 g/liter respectively in FIG. 1 to FIG. 3. FIG. 4 corresponds to a control free of added L-ascorbic acid, which is shown for the sake of comparison. From the results of FIG. 1, it is appreciated that with the addition of 0.5 g, the aqueous ferrous sulfate solution remained substantially stable up to the 7th day but developed changes with the passage of time after the 8th day. As also apparent from FIGS. 2 and 3, the corresponding aqueous ferrous sulfate solutions were increasingly stabilized to significants as L-ascorbic acid was added more and more and in the case of FIG. 3 (added amount: 2 g), the aqueous ferrous sulfate solution did not show any substantial changes until 21th day.

On the other hand, in the case of FIG. 4 which corresponds to the aqueous solution without L-ascorbic acid, no stabilization is observed on the absorption spectrum. Thus, it is clearly demonstrated that the aqueous solution underwent changes with the lapse of time.

EXAMPLE 2

One hundred milliliters of an aqueous solution containing 15% of ferrous sulfate, 2.5% of magnesium oxide, 0.4% of acid clay and 0.4% of natural zeolite (all by wt.%) were diluted to 1 liter under hydrochloric acid condition. To portions of the thus-diluted solution, L-ascorbic acid was added respectively at varied levels up to 20 g to prepare flocculant containing L-ascorbic acid.

On the other hand, a humic acid solution of COD 50 mg/liter was also prepared as sample solution to be treated.

In a beaker, 490 ml of the above sample solution was placed. After stirring it at 150 rpm, 10 ml of one of the above coagulants was added, followed by a pH adjustment with hydrochloric acid or a sodium hydroxide solution to 7.0.

After the pH adjustment, the resultant solution was stirred at 150 rpm for 5-10 minutes and then at 60 rpm for 15 minutes. Upon completion of the stirring, the solution was centrifuged and then filtered through a 5C filter paper to provide a sample. Percent of organic substances removed and remaining iron were measured on the sample. Results are shown in FIG. 5. From these results, it is appreciated that by addition of L-ascorbic acid up to 10 g/liter, the percent of humic acid removed went up considerably. Moreover, the remaining iron was measured by oxidizing the sample with air under neutral to mild alkaline (pH 7-8) conditions in accordance with a method known per se in the art to remove iron.

EXAMPLE 3

(A) Preparation of iron L-ascorbate:

After dissolving 25.7 g of ferrous sulfate hyptahydrate (molecular weight: 278.03) with deionized water to 100 ml, 0.5 g of L-ascorbic acid was added and dissolved to prepare an aqueous bactericidal solution of iron L-ascorbate.

(B) Bactericidal test:

(1) Water to be treated:

Water was collected on July 27, 1982 near Morinosato, Lake Ushiku, Ibaraki for use in the present test.

(2) Procedure of bactericidal test:

A 100 ml portion of the sample water was placed in a 100-ml beaker which had in advance been simply sterilized in dry and hot air. The sample water was agitated vigorously, to which 1 ml of one of the solutions prepared by diluting the above aqueous solution of iron L-ascorbate to 1-100 times. Samples were collected respectively upon elapsed time of 5 minutes, 10 minutes, 15 minutes and 30 minutes. In a manner which is described below, culturing tests were carried out using deoxychlolate culture medium to determine the numbers of colonies of Escherichia coli.

(3) Procedure of culturing tests:

When a sample was expected to contain 300 colonies or more of Escherichia coli per milliliter, 9 ml or 99 ml of a phosphate-buffered aqueous diluent was added to 1 ml of the sample to dilute it. The sample was diluted further when needed, thereby preparing a diluted sample capable of providing 30-300 colonies of Escherichia coli per milliliter after culturing.

Thereafter, 1 ml of the sample was placed in a sterilized Petri dish, to which about 10 ml of deoxycholate culture medium which had been kept at about 48° C. subsequent to its heating and dissolution was added. Then, the Petri dish was shaken to mix the culture medium thoroughly with the sample. When the resultant mixture was spread all over the sterilized Petri dish, the Petri dish was left over horizontally so as to allow the mixture to coagulate. After the coagulation of the mixture, 5-10 ml of deoxycholate culture medium was added further to over the entirety of the coagulated surface, followed by its coagulation as an ovelaid layer.

After the coagulation, the sterilized Petri dish was turned upside down and placed in an incubator, in which the sample was cultured at 36±1° C. for 18-20 hours. Red to Crimson colonies which had occurred on the culture medium and had substantially the same shape were counted. Their average number was then determined to show the number of colonies per ml of the sample. In the case of a diluted sample, a sterilized Petri dish resulted in the occurrence of 30-300 colonies was taken out and the number of colonies per ml of the sample was determined.

(C) Results of bactericidal tests:

The percentage of remaining live bacteria was obtained by determining the proportion (%) of the number of colonies of Escherichia coli in each steritized sample to the number of colonies of Escherichia coli in the untreated water. The relationship between the time (min.) of bactericidal treatment by aqueous iron L-ascorbate solutions of various concentrations and percent remaining live bacteria is shown in FIG. 6.

From the results shown in the figure, the bactericidal efect of ascorbic acid is not observed to any significant degree at the iron ascorbate concentration of 0.01% or so even when a contact time period of 30 minutes was given. However, remarkable effects were observed with concentrations of 0.1% and up. Its sterilizing activity has been found to increase further when added at 1%. These effects cannot be expected from any iron(II) solution. Furthermore, no bactericidal effects can be exhibited with ascorbic acid concentrations of such low levels. As demonstrated above, an addition of iron ascorbate in such a small amount of 0.1% or so can colonies of Escherichia coli without secondary influence. It is thus understood that the above effects, which are not extremely strong, can be used widely for many purposes.

EXAMPLE 4

(A) Preparation of an antiseptic preservative material impregnated with iron L-ascorbate:

Using water, 27.5 g of ferrous sulfate heptahydrate (molecular weight: 278.03) was dissolved to 100 ml. Then, 0.5 g of L-ascorbic acid was added and dissolved to prepare an undiluted aqueous iron L-ascorbate solution.

Thereafter, the undiluted solution was diluted to 5 times. The thus-diluted solution was then sprayed by a sprayer on the entire front and back surfaces of each of kraft paper bags (33.2 cm long and 24 cm wide). After spraying the solution to 15 wt.%, the bags were dried at room temperature.

(B) Freshness-maintaining tests:

Untreated kraft paper bags were provided for the sake of comparison, along with the above-described kraft paper bags subjected to impregnation with iron L-ascorbate. Newly-bought commercial boiled fish paste (product of Marumata Kamaboko Seizo Yugen Kaisha; 220 g), frozen (and thawed) prawns (85 g) and seedless grapes or Kyoho grapes (120 g) were respectively packed and sealed in both of the bags. At room temperature (20° C.), changes in the freshness of each foods along the passage of time and development of rotting (mold, slime, putrid smell) were compared and observed. Results are shown in the following table.

From the results in the following table, it is envisaged that according to this invention, boiled fish paste, seedless grapes and Kyoho grapes can be preserved for a longer period by about 7 more days on average than the comparative examples. Even in the case of frozen prawns, the present invention allows it to last more as many as about 5 more days on average compared with the comparative examples.

                                      TABLE 2                                      __________________________________________________________________________     Foods         1st day 2nd day 3rd day  4th day 5th day 6th                     __________________________________________________________________________                                                            day                     Boiled This    ○1  No change                                                                  No change                                                                              No change                                                                               No change                                                                              No change                                                                              No change               fish   invention                                                               paste  Comparative                                                                            ○2  No change                                                                  No change                                                                              With mold occur-                                                                        A little yellow                                                                        yellow mold                                                                            Black spot                     example                red on the base                                                                         mold occurred                                                                          spread little                                                                          occurred on                                           plate            little  the base plate          Frozen This    ○1  No change                                                                  No change                                                                              No change                                                                               No change                                                                              No change                                                                              Slime occurred          (and thawed)                                                                          invention                                       on the surface          prawns Comparative                                                                            ○2  No change                                                                  A little                                                                               Slime occurred                                                                          Putrid smell                                                                           Both putrid                                                                            Putrid smell                   example        putrid smell                                                                           on the surface                                                                          became strong-                                                                         smell and                                                                              and slime both                                                 er      slime spread                                                                           aggravated,                                                                    shape changed           Seedless                                                                              This    ○1  No change                                                                  No change                                                                              No change                                                                               No change                                                                              No change                                                                              No change               grapes invention                                                                      Comparative                                                                            ○2  No change                                                                  No change                                                                              Stalks browned                                                                          Brown color                                                                            Stalks browned                                                                         Brown parts of                 example                         spread over                                                                            severely                                                                               stalk turned                                                   stalks and      gradually to                                                   grapes lost     black                                                          luster                                  Kyoho  This    ○1  No change                                                                  No change                                                                              No change                                                                               No change                                                                              No change                                                                              No change               grapes invention                                                                      Comparative                                                                            ○2  No change                                                                  No change                                                                              Grape sur-                                                                              Stalks became                                                                          Grapes became                                                                          Grape shape                    example                faces changed                                                                           black   soft    changed                                               in color                                         __________________________________________________________________________              Foods         7th day 8th day 8th day 9th day 10th                    __________________________________________________________________________                                                            day                              Boiled This   No change                                                                              No change                                                                              No change                                                                              No change                                                                              White mold                       fish   invention                              occurred                         paste  Comparative                                                                           Green mold                                                                             Mold of vari-                                                                          Mold of Mold of Mold of                                 example                                                                               occurred on the                                                                        ous colors                                                                             various colors                                                                         various colors                                                                         various colors                                 base plate                                                                             spread  spread  spread  spread                           Frozen This   No putrid                                                                              Slight putrid                                                                          Slight putrid                                                                          Slime occurr-                                                                          Surface slime                    (and thawed)                                                                          invention                                                                             smell   smell occurred                                                                         smell occurred                                                                         ed on the                                                                              and putrid                       prawns                                face and                                                                               smell aggrava-                                                         rid smell                                                                              ted further                                                            somewhat agg-                                                                  ravated                                         Comparative                                                                           Putrid smell                                                                           Putrid smell                                                                           Putrid smell                                                                           Putrid smell                                                                           Putrid smell                            example                                                                               and slime both                                                                         and slime both                                                                         and slime both                                                                         slime both                                                                             and slime both                                 aggravated,                                                                            aggravated,                                                                            aggravated,                                                                            aggravated,                                                                            aggravated,                                    shape changed                                                                          shape changed                                                                          shape changed                                                                          shape changed                                                                          shape changed                    Seedless                                                                              This   No change                                                                              No change                                                                              No change                                                                              No change                                                                              Stalk ends                       grapes invention                              turned to                                                                      brown                                   Comparative                                                                           Green parts                                                                            Grape shapes                                                                           Grape shapes                                                                           Grape shapes                                                                           Rotting of                              example                                                                               of stalk                                                                               changed changed changed and                                                                            grapes                                         shrunk down             grapes rotted                                                                          spread                                         little by                                                                      little                                                           Kyoho  This   No change                                                                              No change                                                                              No change                                                                              No change                                                                              Some changes                     grapes invention                              occurred on                                                                    the skins of                                                                   grapes                                  Comparative                                                                           White mold                                                                             Mold spread                                                                            Mold spread                                                                            White mold                                                                             Holes formed                            example                                                                               occurred on                                                                            on the skins                                                                           on the skins                                                                           gradually                                                                              in grapes                                      the skins of                                                                           of grapes                                                                              of grapes                                                                              tinged                                                 grapes                                                  __________________________________________________________________________

EXAMPLE 5

After dissolving 27.5 g of ferrous sulfate heptahydrate (molecular weight: 278.03) in water to form 100 ml of a solution, 0.5 g of L-ascorbic acid was added to and dissolved in the solution to prepare an undiluted aqueous solution of iron L-ascorbate.

Thereafter, the undiluted aqueous solution of iron L-ascorbate was diluted to a 10 times of volume with water to prepare a liquid deodorant.

Then, 10 g portions of fowl droppings were placed respectively in two scrubbing bottles (each 100 ml in volume). Fifty milliliters of purified water were added to one of the scrubbing bottles and 50 ml of the liquid deodorant to the other scrubbing bottle. The scrubbing bottles were allowed to stand for 24 hours in an incubator of 37° C. After that, gases produced respectively in the scrubbing bottles were each purged out with 20 liters of pure air. They were collected respectively in bags and the amounts of hydrogen sulfide, methyl mercaptan and ammonia in each of the gases (deodorized gas and untreated gas) were measured. Measurement results are shown in Table 3.

EXAMPLE 6

Granular activated carbon (produced by a method known per se in the art, namely, extrusion-forming a mixture which contained 20 parts by weight of commercial by available powdery activated carbon, 20 parts by weight of zeolite and 60 parts by weight of bentonite and then drying; grain sizes: 1.5-2.5 mm) was impregnated with 15 wt.% of the undiluted aqueous solution of iron L-ascorbate, which was prepared in Example 5. After the impregnation, the granular activated carbon was dried at room temperature for 24 hours to prepare a granular deodorant.

On the other hand, 20 g of fowl droppings was taken in a scrubbing bottle (100 ml in volume), followed by an addition of 100 ml of purified water. After allowing the scrubbing bottle to stand for 24 hours in an incubator of 37° C., gases produced in the scrubbing bottle were purged out by 100 ml of pure air to collect them in a bag. Thereafter, 20 g of the above granular doedorant was packed in a glass tube, into which 20 liters of the gas was caused to flow as an offensive odor source from the bag at a flow rate of 2-3 liters/min. The thus-treated gas was then collected in a bag to measure offensive odor components in the bag.

Results are given in Table 3.

From the results of Table 3, it is apparent that the liquid or granular deodorant of this invention shows extremely good deodorizing effects against each of hydrogen sulfide, methyl mercaptan and ammonia.

                  TABLE 3                                                          ______________________________________                                                       Concentration of                                                               offensive odor                                                                 component (ppm)                                                                            After    Rate of                                     Offensive odor  Untreat-  treat-   deodoriza-                                  component       ed        ment     tion (%)                                    ______________________________________                                         Example                                                                               Hydrogen sulfide                                                                            38.2      0.04   99.9                                      1      Methyl mercaptan                                                                            36.1      0.02   99.9                                             Ammonia      273       0.33   99.9                                      Example                                                                               Hydrogen sulfide                                                                            25.7       0.01> >99.9                                     2      Methyl mercaptan                                                                            7.91       0.01> 99.9                                             Ammonia      250       0.01   >99.9                                     ______________________________________                                          Note:-                                                                         Measuring of the offensive odor components were carried out in the             following manner:                                                              .sup.1 Hydrogen sulfide and methyl mercaptan: Quantitatively analyzed by       gas chromatography.                                                            .sup.2 Ammonia: Subsequent to its collection in a liquid ammonia absorben      (1/50N H.sub.2 SO.sub.4 solution), the amount of ammonia in the liquid         ammonia absorbent was quantitatively analyzed by absorptiometry.         

EXAMPLE 7

The undiluted aqueous solution of iron L-ascorbate, which had been prepared three months ago in Example 5, was diluted with tap water to a twice volume of the undiluted aqueous solution. The resultant solution was sprayed to filter papers of 15 cm across ("Toyo Roshi-No. 5C") to give predetermined spray weights to the respective filter papers. The thus-sprayed filter papers were then dried to prepare paper-like deodorants bearing iron ascorbate respectively in adhered and dried weights of (a) 0.38 g, (b) 0.39 g, (c) 0.37 g and (d) 0.48 g.

On the other hand, a 25% aqueous ammonia solution was diluted 4 times to prepare an aqueous ammonia solution. After impregnating different filter papers each with 1 ml of the latter ammonia solution, the thus-impregnated filter papers were placed respectively in 5 plastic containers each having an internal volume of 500 ml. Thereafter, the paper-like deodorants which were the filter papers (a)-(d) were placed either in suitable combinations or singly as a one half portion or one quarter portion respectively in four of the plastic containers. Then, all the five plastic containers were hermetically sealed and then allowed to stand for predetermined time periods. Upon an elapse of each predetermined time periods, changes in offensive odor were investigated.

Investigation results are shown in Table 4.

From the results given in Table 4, it is appreciated that the paper-like deodorants according to the present invention exhibit excellent deodorizing activities against the offensive odor of ammonia.

                  TABLE 4                                                          ______________________________________                                         Deodorant  Ammonia smell                                                       Run  (filter                       24 hours                                    No.  paper)    1 hour later                                                                              3 hours later                                                                           later                                       ______________________________________                                         1    (a) + (b) No offensive                                                                              No offensive                                                                            No offensive                                               odor       odor     odor                                        2    (c)       Extremely  No offensive                                                                            No offensive                                               small offen-                                                                              odor     odor                                                       sive odor                                                       3    1/2 (d)   No offensive                                                                              No offensive                                                                            No offensive                                     (one half odor       odor     odor                                             portion)                                                                  4    1/4 (d)   Strong     Strong   Strong offen-                                    (one quar-                                                                               offensive  offensive                                                                               sive odor                                        ter portion)                                                                             odor       odor     (but somewhat                                                                  milder than                                                                    before)                                     5    Not       Strong     Strong   Strong offen-                                    inserted  offensive  offensive                                                                               sive odor                                                  odor       odor                                                 ______________________________________                                    

EXAMPLE 8

(A) Preparation of freshness-preserving agent:

Using water, 27.5 g of ferrous sulfate heptahydrate (molecular weight: 2778.03) was dissolved to 100 ml, followed by an addition and dissolution of 0.5 g of L-ascorbic acid to prepare an undiluted aqueous solution of iron L-ascorbate.

Then, this undiluted aqueous solution was diluted 50 times with water to prepare a freshness-preserving agent.

(B) Freshness preserving tests:

Five milliliter portions of the above freshness-preserving agent were sprayed respectively to spinach (100 g), banana (one piece, 115 g) and pork (100 g) each of which was newly bought from the market. They were then stored hermetically in respective polyethylene-made transparent bags (30 cm×25 cm) at room temperature (20° C.). Changes in the freshness of the foods and occurrence of rotting (slime, putrid smell) were observed with the lapse of time. Another test was conducted in parallel, without the treatments.

From results given in the following table, it is possible to envisaged such advantageous effects over the comparative example that use of the freshness-preserving agent allows spinach to keep its freshness for 4-5 more days, and banana to restore its original green skin from its once-yellowed skin and its texture to remain firm for 5-6 more days compared with the comparative example. Turning to the pork, it lasted for 3-4 more days compared with the comparative example.

By the way, an aqueous solution of L-ascorbic acid (10 wt.%) was also sprayed to spinach, banana and pork in the same manner as in the above tests. Test results were substantially the same as those given below for comparative example in the following table. Thus, no freshness-preserving effect was observed.

                                      TABLE 5                                      __________________________________________________________________________     Foods       1st day                                                                               2nd day   3rd day  4th day   5th day                        __________________________________________________________________________     Spinach                                                                              This  No change                                                                             No change No change                                                                               No change No change                            invention                                                                      Compar-                                                                              No change                                                                             No change Green color                                                                             Leaves some-                                                                             Leave color                          ative                  of leaves                                                                               what shrunk                                                                              changed little                       example                reduced            by little from                                                                 green to brown                 Banana                                                                               This  No change                                                                             No change Skin surface                                                                            Skin surface                                                                             the change of                        invention              rendered black-                                                                         changed gradual-                                                                         skin surface                                                ish      ly from yellow                                                                           from yellow to                                                       to green  green accelerat-                                                               ed                                   Compar-                                                                              No change                                                                             No change Brown spots                                                                             Brown spots                                                                              Stem was also                        ative                  developed on                                                                            spread on skin                                                                           turned to brown                      example                skin surface                                                                            surface                                  Pork  This  No change                                                                             No change Slime occurred                                                                          Surface slime                                                                            Slime on the                         invention              on the surfaces                                                                         aggravated                                                                               surfaces, some                                                                 putrid smell                                                                   occurred                             Compar-                                                                              No change                                                                             Slime occurred on                                                                        Surface slime,                                                                          Surface slime,                                                                           Surface slime,                       ative        the surfaces,                                                                            yellow color of                                                                         yellow color of                                                                          yellow color of                      example      fatty parts turn-                                                                        fatty parts and                                                                         fatty parts and                                                                          fatty parts and                                   ed to yellow some                                                                        putrid smell,                                                                           putrid smell, all                                                                        putrid smell,                                     putrid smell                                                                             all aggravated                                                                          aggravated fur-                                                                          all aggravated                                    occurred           ther      still further                  __________________________________________________________________________     Foods     6th day   7th day   8th day   9th day  10th day                      __________________________________________________________________________     Spinach                                                                             This No change No Change Some black spots                                                                         Black spots                                                                             Leaf shapes not                    invention                appeared on                                                                              occurred in                                                                             changed but                                                 leaves    parts of leaves                                                                         black spots                                                                    spread                             Compar-                                                                             Leaf surfaces                                                                            Leaves turned to                                                                         Browning and                                                                             Browning and                                                                            Browning and                       ative                                                                               dried and leaf                                                                           brownish, and                                                                            shape changes of                                                                         shape changes of                                                                        shape changes of                   example                                                                             shapes changed                                                                           leaf shapes                                                                              leaves    leaves, further                                                                         leaves, aggravat-                                 changed further                                                                          aggravated                                                                               aggravated                                                                              ed still further              Banana                                                                              This Green color render-                                                                      Black spots                                                                              Green color of                                                                           Green color                                                                             When the skin                      invention                                                                           ed darker on skin                                                                        occurred locally                                                                         stem darkened                                                                            darkened all                                                                            was peeled off,                         surface   on skin surface     over the banana                                                                         the inside was                                                        and the texture                                                                         white and tasty,                                                      remained firm                               Compar-                                                                             Both skin and stem                                                                       Brown color domi-                                                                        Skin surface                                                                             Skin surface be-                                                                        The inside was                     ative                                                                               became less yellow                                                                       nated on both                                                                            became more brown                                                                        came still more                                                                         slightly yellow-                   example                                                                             and more brown                                                                           skin and stem, &                                                                         and black brown and black,                                                                        ish with some                                     black color         and the texture                                                                         localized brown                                   appeared            was soft slime, but tasty              Pork This Surface slime and                                                                        Visual observa-                                                                          --        --       --                                 invention                                                                           putrid smell occur-                                                                      tion impossible                                                      red. Fatty parts                                                               turned yellow                                                             Compar-                                                                             Surface slime, yel-                                                                      Visual observa-                                                                          --        --       --                                 ative                                                                               low color of fatty                                                                       tion impossible                                                 example                                                                             parts and putrid                                                               smell, all aggra-                                                              vated further                                                        __________________________________________________________________________

EXAMPLE 9

(A) Preparation of antiseptic preservative material impregnated with iron L-ascorbate:

After dissolving 27.5 g of ferrous sulfate heptahydrate (molecular weight: 278.03) to 100 ml with water, 0.5 g of L-ascorbic acid was added and dissolved to prepare an undiluted aqueous solution of iron L-ascorbate.

Granular activated carbon (produced by a method known per se in the art, namely, extrusion-forming a mixture which contained 20 parts by weight of commercial available powdery activated carbon, 20 parts by weight of zeolite and 60 parts by weight of bentonite and then drying; grain sizes: 1.5-2.5 mm) was impregnated with 15 wt.% of the above-prepared undiluted aqueous solution of iron L-ascorbate. After the impregnation, the granular activated carbon was dried at room temperature for 24 hours to prepare a granular deodorant.

(B) Freshness preservation tests:

Spinach (100 g), banana (one piece, 110 g) and pork (100 g), each of which was newly bought from the market, were packed respectively in three polyethylene-made transparent bags (about 30 cm×25 cm). After inserting five milliliter portions of the granular freshness-maintaining agent, prepared above in (A), were placed respectively in the bags. Thereafter, the openings of the bags were hermetically sealed. They were then stored at room temperature (about 20° C.). Changes in the freshness of the foods and occurrence of rotting (slime, putrid smell) were tested along the passage of time. Another test, which was exactly the same as the above test except for the exclusion of the granular freshness-preserving agent, was conducted for the sake of comparison. Test results are shown in the following table.

From the results given in the following table, it is apparent that the freshness-preserving agent of this invention can exhibit excellent freshness-preserving activities for each of spinach, banana and pork.

                                      TABLE 6                                      __________________________________________________________________________     Foods       1st day                                                                               2nd day    3rd day    4th day    5th                        __________________________________________________________________________                                                         day                        Spinach                                                                              This  No change                                                                             No change  No change  No change  No change                        invention                                                                      Compar-                                                                              No change                                                                             No change  Green color of                                                                            Leaves shrunk                                                                             Green color of                   ative                   leaves reduced                                                                            slightly   leaves turned                    example                                       little by little                                                               to brown                   Banana                                                                               This  No change                                                                             No change  No change  No change  Slightly brown                   invention                                     spots occurred                   Compar-                                                                              No change                                                                             No change  Brown spots                                                                               The brown spots                                                                           Stem changed to                  ative                   occurred on skin                                                                          spread on skin                                                                            brown too                        example                 surface    surface                               Pork  This  No change                                                                             No change  Slime occurred on                                                                         Surfaces slime                                                                            Surface slime,                   invention               surfaces and                                                                              and yellow color                                                                          yellow color of                                          fatty parts turn-                                                                         of fatty parts                                                                            fatty parts and                                          ed to yellow                                                                              gradually aggra-                                                                          putrid smell, all                                                   vated, some                                                                               aggravated                                                          putrid smell                                Compar-                                                                              No change                                                                             Slime developed                                                                           Surface slime,                                                                            Surface slime,                                                                            Surface slime,                   ative        on surfaces and                                                                           yellow color of                                                                           yellow color of                                                                           yellow color of                  example      fatty parts turn-                                                                         fatty parts and                                                                           fatty parts and                                                                           fatty parts and                               ed to yellow,                                                                             putrid smell, all                                                                         putrid smell, all                                                                         putrid smell, all                             some putrid smell                                                                         aggravated aggravated further                                                                        aggravated                 __________________________________________________________________________                                                         further                    Foods       6th day   7th day   8th day   9th day   10th                       __________________________________________________________________________                                                         day                        Spinach                                                                              This  Green color of                                                                           Green color of                                                                           Green color of                                                                           Leaves shrunk                                                                            Shrinkage and brown              invention                                                                            leaves reduced                                                                           leaves reduced                                                                           leaves reduced                                                                           and partly turn-                                                                         parts of leaves                                            and partly turned                                                                        ed to brown                                                                              spread a little,                                           to brown            leaf shapes changed              Compar-                                                                              Leaf surfaces dried                                                                      The browning and                                                                         The browning and                                                                         The browning and                                                                         The browning and                 ative and leaf shapes                                                                          shape changes of                                                                         shape changes of                                                                         shape changes                                                                            shape changes of                 example                                                                              changed   leaves, aggravat-                                                                        leaves, aggravat-                                                                        leaves, aggravat-                                                                        leaves, intensified                              ed        ed further                                                                               ed still further                     Banana                                                                               This  Slightly brown                                                                           Brown spots spread                                                                       Brown spots                                                                              Brown spots                                                                              The inside was                   invention                                                                            spots occurred                                                                           gradually spread gradually                                                                         spread but the                                                                           light-yellowish and                                                  majority of skin                                                                         free of slime                                                        surface remained                                                               still yellow                               Compar-                                                                              Both skin and stem                                                                       Both skin and                                                                            Brown and black                                                                          Brown and black                                                                          The inside turned                ative became less yellow                                                                       stem turned more                                                                         spots expanded on                                                                        spots expanded                                                                           to light-yellowish               example                                                                              and more brown                                                                           to brown and                                                                             the skin surface,                                                                        the skin surface,                                                                        localized brown                                  black color         and the inside                                                                           slime, but tasty                                 appeared            became soft                          Pork  This  Surface slime,                                                                           Visual observa-                                                                          --        --        --                               invention                                                                            yellow color of fat-                                                                     tion impossible                                                      ty parts and putrid                                                            smell, all aggravat-                                                           ed                                                                       Compar-                                                                              Surface slime,                                                                           Visual observa-                                                                          --        --        --                               ative yellow color of                                                                          tion impossible                                                example                                                                              fatty parts and                                                                putrid smell, still                                                            aggravated                                                         __________________________________________________________________________

EXAMPLE 10

(A) Production of ice blocks:

Using water, 27.5 g of ferrous sulfate heptahydrate (molecular weight: 278.03) was dissolved to 100 ml, in which 0.5 g of L-ascorbic acid was added and dissolved to prepare an undiluted aqueous solution of iron L-ascorbate. This undiluted aqueous solution was diluted to 300 times of volume with water. Using the thus-diluted aqueous solution, ice blocks having sizes of about 1-2 cm were produced.

(B) Freshness-preserving tests on fish and shellfish:

The above ice blocks were filled to a thickness of about 10 cm in a foamed polystyrene box (50 cm long, 30 cm wide and 30 cm deep). A paper sheet was laid over the ice blocks, on which various fish and shellfish newly bought from a market were placed. Then, the box was covered by a lid and then stored for 5 days. The temperature in the box was 3° C. for lower. As a control, fish and shellfish were stored for 5 days in a foamed polystyrene box in the same manner, using ordinary ice. Fresh fish and shellfish newly bought from the market were divided to equal half portions, which were provided as samples of the same conditions for both tests respectively.

Upon an elapsed time of 5 days, the lids were removed and the freshness of the fish and shellfish in both boxes were compared and evaluated by a panel of 10 monitors on the basis of the appearance of fish meat, the firmness of meat, feeling to eat, taste and the like. Test results are summarized in the following table.

                                      TABLE 7                                      __________________________________________________________________________                      Evaluation on freshness after stored for 5 days                                Appearance (color, luster) &                                  Fish or shellfish                                                                        Ice used                                                                              firmness of meat                                                                               Feeling to eat, taste,                        __________________________________________________________________________                                      etc.                                          Tuna fillet                                                                              Invention ice                                                                         Good brightness, and                                                                           No significant differ-                        (100 g)   blocks springy and firm texture                                                                       ence between two                                        Ordinary ice                                                                          No brightness and no                                                                           samples for taste                                              springy nature, soft texture                                  Fillet of young                                                                          Invention ice                                                                         Good brightness. without                                                                       No fishy smell                                yellowtail                                                                               blocks discoloration, red parts remained                             (100 g)          with vivid crimson color                                                Ordinary ice                                                                          Brightness lost. Red parts                                                                     Fishy smell                                                    turned to brown                                               Shrimps (produce                                                                         Invention ice                                                                         No substantial change                                                                          Extremely slight fishy                        of Mexico,                                                                               blocks                 smell                                         frozen) (100 g)                                                                          Ordinary ice                                                                          No substantial change                                                                          Strong fishy smell                            Octopus   Invention ice                                                                         Firm texture    Good in both feeling to                       (100 g)   blocks                 bite and taste                                          Ordinary ice                                                                          Soft texture    Poor feeling to bite                          Saurel (100 g)                                                                           Invention ice                                                                         Good brightness and color                                                                      Slight fishy smell                                      blocks                                                                         Ordinary ice                                                                          No brightness   Strong fishy smell                            Flounder (100 g)                                                                         Invention ice                                                                         Good brightness Good feeling to bite                                    blocks                                                                         Ordinary ice                                                                          Slightly discolored                                           Pen shell meat                                                                           Invention ice                                                                         No substantial change                                                                          Good feeling to bite                          (100 g)   blocks                                                                         Ordinary ice                                                                          No substantial change                                                                          Poor feeling to bite                          __________________________________________________________________________

Totally judging from the results in the above table, it is understood that the freshness was significantly reduced in the control test, in which ordinary ice was used, although the storage conditions corresponded to the winter; and the present invention is able to avoid such freshness reduction and hence to preserve the freshness of fish and shellfish under good conditions with good liveliness and feeling to bite but without fishy smell. 

We claim:
 1. An oxidation-resistant chemical composition effective as a deodorizing agent, a bactericidal agent, a food preserving agent, or a pollutant coagulating agent, which comprises divalent iron ions and L-ascorbic acid, said L-ascorbic acid being present in an amount of 2 to 10 parts by weight per 100 parts by weight of the divalent iron ions, expressed in terms of metallic iron.
 2. The oxidation-resistant chemical composition of claim 1 in the form of an aqueous solution wherein the divalent iron ions are present in a concentration of from 0.15 weight percent, calculated in terms of the metallic iron, up to the solubility of the divalent iron ions in the aqueous solution.
 3. A solid material impregnated with the composition of claim
 2. 4. The oxidation-resistant chemical composition of claim 2 wherein the chemical composition solution is a deodorant wherein the total concentration of L-ascorbic acid and divalent iron compound is present in the aqueous solution in a concentration of 0.1 to 30 weight percent.
 5. The oxidation-resistant chemical composition of claim 3 wherein the solid material is selected from the group consisting of paper, synthetic paper, a fabric, a non-woven fabric, and a porous material.
 6. The oxidation-resistant chemical composition of claim 5 wherein the porous material is selected from the group consisting of activated carbon, zeolite, bentonite, kaolin, pearlite sepiolite, diatomaceous earth, silica and alumina.
 7. The oxidation-resistant chemical composition of claim 3 wherein the total amount of L-ascorbic acid and divalent iron ions to be carried by the solid material is 0.5 to 20 parts by weight per 100 parts by weight of the solid material.
 8. The oxidation-resistant chemical composition of claim 1, wherein the divalent irons and ascorbic acid form a complex.
 9. An aqueous coagulant solution for water pollutants comprising L-ascorbic acid and an iron (II) compound in a total concentration of 0.01 to 20 weight percent based on the weight of the coagulant solution. 